1. Field of the Invention
The present invention relates generally to a driving wheel structure for a motor vehicle employing an in-wheel motor and, more particularly, to a compact driving wheel structure for a motor vehicle that can afford to have a high freedom in design while realizing a function of high performance suspension.
2. Background of the Invention
Conventionally, driving wheel structures for a motor vehicle employing an in-wheel motor arrangement are known in the art, one example of which being disclosed in Japanese Patent Application Publication No. JP-A-2005-119548.
Japanese Patent Application Publication No. JP-A-2005-119548 describes a suspension device and a suspension arm arrangement used in a driving wheel employing an in-wheel motor structure to provide an anti-dive control, a damping control and an anti-roll control by virtue of a motor drive control.
Taking advantage of the up-down movement (rising and sinking) of a vehicle body that occurs when accelerating or decelerating, the conventional device described in Japanese Patent Application Publication No. JP-A-2005-119548 is adapted to induce a damping action or an anti-roll action by performing acceleration and deceleration in response to the vehicle body up-down movement or a rolling movement. However, this device fails to resolve the problem that the vehicle body undergoes an up-down movement when accelerating and decelerating.
As a technique for suppressing the up-down movement during acceleration and deceleration to thereby optimize a pitch attitude, it may be theoretically contemplated that, by elongating a trailing arm for instance, the momentary center of rotation (swing movement) of a body-side member (suspension arm) to which the stator of a motor is attached may be located as far away as possible from the corresponding driving wheel in the longitudinal direction of the vehicle at the time of braking or driving. Another theoretically feasible solution may be to keep the momentary rotation center as close to the ground as possible (at least lower than an axle shaft).
If, however, the mounting position of the suspension arm on the vehicle body or the length of the suspension arm is restricted, the freedom in the layout design is degraded and the space utilizing efficiency is reduced as well.
Further, in the conventional device described in Japanese Patent Application Publication No. JP-A-2005-119548, due to its structural features, the force acting in the longitudinal direction is necessarily applied to the vehicle body during a damping control process, possibly accompanied with unintended acceleration, deceleration or vibration.
Moreover, in the conventional device described in Japanese Patent Application Publication No. JP-A-2005-119548, due to its structural features, a yaw moment necessarily acts on the vehicle body during an anti-roll control process, resulting in a possible movement of the motor vehicle in an unintended direction.